The present invention relates generally to a medium voltage starter for a chiller unit and, specifically, to a unit mounted, single box, medium voltage solid-state starter for a chiller unit.
In low voltage chiller systems, the starter box for the compressor motor can be mounted directly on the chiller system as discussed in U.S. Pat. No. 4,895,005, which patent is hereby incorporated by reference. However, for a medium voltage chiller system, the starter box for the compressor is typically mounted on the floor either next to the chiller system or in a separate equipment room because of the larger size of the starter box, typically greater than 60 cubic feet.
One of the reasons for mounting the starter box on the floor for medium voltage chiller systems is that medium voltage is typically ten times greater than low voltage. This larger voltage can create a more difficult working environment because the electrical strike distance and creep distance are much longer than in a low voltage environment. These longer distances require larger electrical spacings and protective equipment for the mounting of components resulting in a larger starter box. In addition, the devices used for the medium voltage starter box must be designed for the larger voltages, which also contributes to a larger starter box.
One attempt that has been made to mount medium voltage starter components on the chiller system is described in U.S. Pat. No. 6,679,076 to Duga et al. The Duga et al. system discusses the use of two starter boxes mounted on the chiller system for specific sizes of chiller systems and with specific unit mounting locations. The two starter boxes in the Duga et al. system are interconnected by wiring conduit. One major drawback of the two box arrangement in the Duga et al. system is that it involves complicated and expensive wiring arrangements in order to interconnect the boxes and the motor.
Therefore, what is needed is a single box, medium voltage solid-state starter for a chiller system that can be mounted on the chiller unit.